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Elemental characterization and moisture content of coal

Elemental characterization of coal is fundamental in geology and mining for determining the chemical composition. Knowing the content of key elements such as carbon, hydrogen, sulfur, nitrogen, oxygen is crucial for resource valuation, and process control in extractive metallurgy.

The purpose is also to assess the fuel value and environmental impact of coal. Carbon and hydrogen directly influence the calorific value (energy content); sulfur contributes to SO₂ emissions on combustion and must be controlled. These parameters inform whether a coal meets specifications for power generation or steelmaking, and they help in resource grading and mine planning

Instruments operate according to ASTM/ISO methods. These standards ensure that the analyzers provide accurate, repeatable results in line with industry norms. For example, Eltra’s high-temperature CS-r analyzer yields sulfur results compliant with ISO 19579:2006 (Solid mineral fuels – Determination of sulfur by IR spectrometry) and ASTM D 4239-18 (Standard Test Method for Sulfur in Coal and Coke).

Also moisture content in coal is quite important determination done by Thermogravimetric Analysis (TGA), where the mass loss observed upon controlled heating corresponds to the evaporation of inherent and surface water, following standard methods such as ASTM D 7582-24 .

 

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Ultimate analysis standard methods on coal

Ultimate analysis of coal is standardized in both ISO and ASTM methods, sometimes referred to as “elemental analysis” or part of a coal’s “ultimate” properties. ASTM D4239-18 and ASTM D 5016-24 & ASTM D 6316-17 cover sulfur by high-temperature combustion/IR detection. Industry literature emphasizes the importance of these measurements for coal grading. For instance, hydrogen content contributes to water formation during combustion, reducing usable heat, so it’s directly tied to coal’s effective calorific value. Measuring these elements precisely with analyzers like Eltra’s ensures that mining operations and coal buyers have reliable data on fuel quality.

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Sulfur Determination for Mineral Grade Evaluation

Many base and precious metal ores, including copper, lead, and zinc, occur as sulfide minerals such as chalcopyrite (CuFeS₂), galena (PbS), and pyrite (FeS₂). Measuring sulfur content in these geological samples is a proven approach for mineral grade evaluation, as sulfur concentration typically correlates with sulfide abundance and therefore with potential metal yield. In copper mining, for example, sulfur determination provides an indirect but robust proxy for copper grade. Since chalcopyrite has a fixed Cu:S ratio, higher sulfur values indicate greater chalcopyrite content and, consequently, higher copper potential. This makes sulfur analysis a cost-effective and rapid tool for exploration campaigns, resource evaluation, and process optimization.

Accurate sulfur determination is performed with ELTRA’s CS-i carbon/sulfur analyzers, which employ high-temperature induction combustion (>2000 °C) in an oxygen atmosphere. The sulfur released as SO₂ is quantified by infrared detection, ensuring precise and reproducible results even for refractory sulfide minerals. The method accepts relatively large sample weights (200–300 mg), which improves representativity in heterogeneous ores. Standardized procedures—such as ISO 15178:2000 & 4689-3:2017 for soils and ores, ASTM E1915-20 for metal-bearing ores, and analogs to ISO 19579:2022 used in fuel analysis—support the reliability and comparability of results across laboratories and projects.

By converting sulfur percentages to approximate mineral or metal content using known stoichiometries, geologists gain a direct link between elemental analysis and economic grade. This makes sulfur determination with ELTRA’s CS-series analyzers an indispensable part of modern exploration, geometallurgy, and quality control workflows, bridging laboratory precision with real-world mining decisions.

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地質学・鉱業ラボを支えるソリューション

QATMの高精度試料調製装置は、地質学や鉱業分野における材料研究の進展に不可欠です。鉱物学的評価から、特殊な惑星科学研究に至るまで、QATMは幅広い地球科学アプリケーションに対応する信頼性の高い高品質な試料調製を実現するための装置と技術を提供します。

Applications in Mining and Mineral Analysis

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Ore Mineral Intergrowth Analysis

適切に作製された薄片は、鉱物ロッキングの特定に不可欠です。鉱物ロッキングとは、鉱物同士が相互に成長し、鉱石処理における粉砕や分離の戦略に影響を与える状態を指します。

Reflected Light Microscopy & Electron Beam Analysis

不透明な鉱物（硫化物や酸化物など）を反射光で観察するためには、研磨片が必要です。これらの研磨面は、電子プローブによる定量分析や、QEMSCANのような自動鉱物分析プラットフォームにとって不可欠です。

Sample Integrity and Preparation Quality

微小亀裂のない、完全で代表性のある表面を得ることは極めて重要です。QATMの真空含浸装置と高精度カッターは、構造の完全性を確保し、最初から最適な前処理を実現します。

Hardness and Wear-Related Studies

通常の試験ではありませんが、特定の鉱物相に対する微小硬さ試験やスクラッチ試験は、粉砕性や摩耗挙動の研究を支援できます。これらの分野で、QATMの硬さ試験装置は相ごとの精密なインサイトを提供します。

鉱業を超える広範な地球科学研究を支援

  • 古生物学：化石の観察や構造研究のための高精度な研磨
  • 隕石学：鉄隕石をエッチングおよび研磨し、分類や起源解析に不可欠なウィドマンシュテッテン構造を露出
  • 惑星地質学：高解像度分析において表面仕上げと完全性が重要となる、地球外試料の調製

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Polished Mounts for Mineral and Ore Analysis

Preparing polished mounts (also known as polished blocks) is a critical step in the analysis of rock, ore, and coal specimens. These mounts enable high-precision observations under reflected light microscopy and are indispensable in various electron beam analyses such as SEM (Scanning Electron Microscopy) and electron microprobe work. Unlike thin sections—which are translucent slices mounted on glass—polished blocks are thicker briquettes or pieces of material featuring a flat, mirror-like surface. They are especially suitable for studying opaque mineral phases that are otherwise invisible in transmitted light.

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Observation of Opaque Minerals

Many ore minerals, including pyrite, chalcopyrite, and galena, are opaque. These must be examined in reflected light using a polished surface to reveal key features such as mineralogy, grain boundaries, exsolution textures, and microfractures.

Quantitative Automated Mineralogy

Systems like QEMSCAN or MLA use SEM/EDS to scan polished surfaces for mapping mineral compositions. These are widely used in mining operations to evaluate mineral liberation and associations, crucial for optimizing processing techniques.

Electron Microprobe Analysis

A polished, smooth surface ensures accurate X-ray detection during microprobe analyses. This is essential for studying zonation, identifying tiny mineral inclusions, and determining detailed chemical compositions.

Coal Rank and Petrographic Analysis

In coal studies, polished pellets are used to measure the reflectance of vitrinite macerals—an essential parameter for classifying coal rank and assessing suitability for coke production.

Fluid Inclusion Microthermometry

For analyzing fluid inclusions, doubly-polished thick sections (polished on both sides) are required. High-quality polishing is crucial to clearly observe tiny inclusions, especially in quartz and ore minerals.

Standards and Best Practices

General Metallography: ASTM E3 outlines standard practices for metallographic sample preparation.

ISO 7404-2 and ASTM D2797 specify preparation methods for coal pellets, including the use of aluminum oxide for final polishing to prevent alteration of reflectance measurements.

Polished mounts are indispensable tools in both academic and industrial geoscience. They bridge the gap between observational and analytical methods, offering a reliable platform for both qualitative and quantitative analysis.

QATM Equipment in Geology and Mining

鉱業分野では：

  • 鉱石の適切な薄片は、鉱物のロッキング（どの鉱物が相互に成長しているか）を明らかにし、粉砕や分離の戦略に影響を与えます。
  • 不透明な鉱石鉱物（硫化物や酸化物など）を識別し、電子プローブや自動鉱物分析（例：QEMSCAN）による分析を行うためには、反射光顕微鏡用の研磨片が必要です。
  • 試料の完全性（亀裂がないこと、代表的な表面であること）を確保することが重要であり、QATMの真空含浸や精密切断はこれに役立ちます。
  • 鉱物に対して硬さ試験やスクラッチ試験を適用し、粉砕性や摩耗との相関を調べる場合があります（通常は行いませんが、研究では特定相の微小硬さが必要になることがあります）。
  • さらに、地質学者は同様の試料調製を古生物学（化石の研磨）、隕石学（鉄隕石をエッチングしてウィドマンシュテッテン構造を露出）、惑星地質試料などにも利用します。

Preserving Petrographic Precision in Coal Oxidation Studies

Understanding coal weathering and oxidation is essential for accurate petrographic analysis and vitrinite reflectance measurement. As highlighted in recent studies, surface alterations during oxidation can significantly affect coal classification and usage potential. QATM's advanced sample preparation solutions—ranging from precision cutting to automated polishing—ensure optimal surface quality for reliable analysis under reflected light microscopy. Whether you're studying natural weathering or simulating oxidation in the lab, QATM systems provide the consistency and control needed for reproducible results. Trust QATM to support your research in coal behavior and carbon material integrity.

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多孔質地質試料の真空含浸

多くの地質材料（例：高い多孔性を持つ砂岩、未固結の土壌、石炭、鉱物精鉱など）は、前処理中に崩れたり、破片が失われる可能性が高く、その主な解決策が樹脂による真空含浸です。 真空含浸では、エポキシ樹脂が孔や亀裂を充填し、試料を安定化・補強します。切断や研磨時の材料損失や気泡形成を防ぎ、確実な前処理を可能にします。

Why it is performed:

  • サンプルの完全性の確保のために：　脆い鉱石や、亀裂を粘土で埋められた風化岩は、乾式切断するだけで崩壊する可能性があります。真空含浸を行わない場合、孔が潰れたり粒子が脱落し、薄片や研磨試料が損なわれるのに対し，真空含浸を用いれば、試料が一体化し、内部構造が顕微鏡観察用に利用できます。
  • 良好な研磨と正確な表現を実現するために：　試料に空孔があると研磨中に軟質材が引きずられるため、凹凸が生じて平坦面が得られません。樹脂で空孔を充填することで連続面が形成され、定量的画像解析や電子プローブ分析に不可欠な平坦研磨が行えます。
  • 粉末試料を固形マウントにするために：　重鉱物分離物やテーリングなどの粉末試料を観察する場合、樹脂と混合し、真空下で鋳込みことで空気が除去され、粒子が確実に固定されます。
  • 真空の役割：真空下では微細な空孔や亀裂内に樹脂が浸透し、空気の閉じ込めによる未充填を防止でき、強固で空隙のないマウントが得られます。

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岩石薄片の調製

標準薄片作製の重要性：　標準薄片は、岩石や鉱物を約30 µmの厚さにスライスし、ガラススライドに固定したものです。透過光顕微鏡や偏光顕微鏡での観察に不可欠なこの技術は、地質学の基盤であり、岩石の鉱物組成、微細構造、組織を詳細に明らかにします。 QATMの装置は、すべての段階のプロセスをサポートします。 ・初期スライスの精密切断 ・均一な厚さを実現する制御研磨 ・光学的透明度を高めるための片面または両面研磨（オプション）

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なぜ薄片が必要か？

  • 鉱物学的分析：多くの鉱物は半透明であり、複屈折、屈折率、消光角などの光学特性を利用した薄片のみ正確に同定できます。
  • 組織の解釈：結晶形態、粒度分布、配列（ファブリック）、累帯構造や変質など、薄片であれば，鉱物粒子相関を明らかにします。
  • 地質履歴の解明：薄片からは岩石の成因を推定できます。例：変成岩の片理、火山岩の斑晶と石基の配置、堆積岩のセメントや空隙。
  • 鉱業での応用：鉱石の薄片は、鉱石鉱物と脈石の共生状態を示し、粉砕や選鉱戦略の立案に役立ちます（不透明鉱物には反射光研磨片が一般的ですが、薄片であれば珪酸塩や炭酸塩染色にも有効）
  • 学術・教育・特殊分析：大学の岩石学実習や流体包有物研究（厚片や両面研磨片が必要）など、標準的な研究用途にも不可欠です。
<br/> QATMの提供する装置： 薄片切断機（または薄片対応ユニバーサルカッター） 薄片プレス（試料とスライドの気泡のない密着を確保） 研磨ディスク（ダイヤモンドカップ）と研磨クロスのラインアップ

Microhardness Testing of Minerals and Rocks Precise Measurement of Mineral and Phase Hardness in Geosciences

Micro-indentation hardness testing—using techniques such as Vickers or Knoop under low loads—is a powerful method for evaluating the hardness of individual mineral grains and phases in geological specimens. While commonly used in metallurgy, this technique is equally valuable in the geosciences. QATM microhardness testers, originally developed under the Qness brand, offer precise, reliable measurement solutions that extend beyond metals to polished rock, ore, coal, and planetary samples.

Key Applications of Microhardness Testing in Geology

 

  • Quantitative Mineral Hardness Characterization Unlike the traditional Mohs scale, which is qualitative, microhardness testing provides numerical values (e.g., Vickers Hardness Number) for mineral hardness. This allows for more accurate comparisons, the detection of subtle differences between visually similar minerals (e.g., calcite vs. aragonite), and even insights into compositional zoning within a single crystal (e.g., core-to-rim changes in garnet).

  • Ore Comminution Studies The hardness of individual mineral phases affects how rocks fracture and grind. Harder minerals may resist fragmentation, remaining as coarse particles and potentially trapping softer or valuable phases. Microhardness data supports modeling of ore fragmentation and optimization of grinding processes.
  • Coal Weathering and Oxidation Monitoring  Research—including early studies by Given & Nandi in the 1970s—has shown that coal microhardness can increase as it oxidizes due to chemical bonding changes. This makes microhardness a useful proxy for assessing coal oxidation and weathering, which impacts its gas content, coke-making quality, and storage stability.
  • Meteorites and Planetary  MaterialsUnderstanding the microhardness of extraterrestrial phases can offer insights into their abrasion resistance, behavior during atmospheric entry, or response to impact events—key considerations in planetary science.
  • Construction Materials (Concrete Aggregates)  Microhardness testing is also used to evaluate the hardness contrast between aggregate particles and the cement matrix. This helps in predicting wear resistance and polishing behavior in applications like industrial flooring.
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Qness 10 / 60 M

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Why our equipment?

  • High-precision indentation at micron scale
  • Automated measurements and imaging for efficient workflows
  • Compatibility with polished geological specimens 
  • Absolute hardness values in MPa or kgf/mm², allowing detailed material comparisons
Even fine distinctions—such as different hardness values in polymorphs or across compositional zones—can be captured with QATM instruments, supporting both research and industrial applications.

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Grain Size Analysis of Sediments and Soils with Laser Diffraction

This application is used for sedimentology studies (e.g., analyzing river, marine, or aeolian sediments), soil science and environmental geology (e.g., understanding contaminants depends on sediment grain sizes).

Grain size distribution reveals information about the depositional environment and material properties in fact can help in interpretating energy conditions of deposition. It is also used in stratigraphy and paleoclimate studies as particle size can indicate wind strength in past climate. In geotechnical engineering soil particle size affects permeability, compaction, and strength. Furthermore regulatory frameworks sometimes require soil particle size analysis for land reclamation or erosion risk assessment.

Traditionally, sieve methods as provided by Retsch are also used, but laser diffraction offers a much faster and detailed measurement across the full range. This has led to many labs adopting laser particle sizers for routine analysis of sediment cores, soil. 

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Laser diffraction from Microtrac offers fast, high-resolution particle size analysis with minimal sample needs. It detects fine particles better than sieves/pipettes and follows ISO 13320 and ASTM B822 standards for accuracy. Studies show good agreement with traditional methods when dispersion is adequate. Its automation, reproducibility, and ability to analyze small or rare samples make it ideal for modern sedimentology and geology labs and geological agencies (like USGS - United States Geological Survey). 

Gas Storage Capacity of Coal and Shale (Methane/CO₂ Adsorption Isotherms)

High-pressure gas adsorption isotherm measurements on coal or shale samples to determine how much gas (methane or carbon dioxide, typically) these rocks can adsorb. This application underpins assessments of coalbed methane (CBM) resources, shale gas capacity, and the viability of CO₂ sequestration in coal seams or shale formations (often coupled with Enhanced Gas Recovery concepts). Understanding how gases interact with coal and shale is critical for energy exploration and carbon management. High-pressure adsorption studies reveal how much gas can be stored, recovered, or sequestered under real reservoir conditions.

Key Applications:


  • Coal mining & CBM exploration: Methane adsorption capacity (Langmuir volume) indicates how much gas a coal seam can hold. Shale gas evaluation: Measuring both methane and CO₂ adsorption provides insight into gas-in-place and preferential sorption (CO₂ often binds more strongly, enabling enhanced methane recovery through CO₂ injection).
  • Carbon sequestration: Adsorption studies determine how much CO₂ can be securely stored in unmineable coal seams or organic-rich shales, with focus on stability and kinetics.

Microtrac’s BELSORP high-pressure systems deliver precise adsorption isotherms up to several MPa, replicating reservoir conditions (0–5 MPa for methane). These instruments support international standards (ISO 18866 in development, ISO 15901-2:2022) and national norms such as China’s GB/T for coal methane sorption. By quantifying parameters like Langmuir volume and pressure, the technique underpins reserve estimation, CO₂-enhanced coalbed methane recovery, and greenhouse gas sequestration strategies. With standard, reliable data, geoscientists can design and optimize reservoir operations—making high-pressure adsorption analysis fundamental for both energy resource development and environmental management. 

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Wollastonite Morphology Analysis

Wollastonite (CaSiO₃) is a naturally occurring chain silicate that crystallizes in acicular (needle-like) forms. Its aspect ratio (length/width) and particle shape distribution critically determine its reinforcing effect in plastics, paints, friction products, and ceramics. Conventional size analysis by sieving or diffraction provides only equivalent spherical diameters and fails to characterize elongated morphologies. Dynamic Image Analysis (DIA) with the Microtrac CAMSIZER enables a quantitative and reproducible assessment of both particle length and thickness, delivering a complete morphology profile.

Why is important to choose DIA analysis?

  • Simultaneous measurement of particle size and shape parameters (length, width, aspect ratio, sphericity).
  • High statistical significance: thousands of particles measured per second for reproducible, representative data.
  • True acicular particle characterization: differentiation of elongated vs. equant grains, impossible with diffraction alone.
  • Non-destructive analysis with real particle images available for verification and documentation.
  • Applicable across mineral processing workflows, from comminution control to quality control of final mineral products.

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Particle Morphology Characterization

DIA simultaneously records thousands of high-resolution images per second, providing length and width distributions, aspect ratio, elongation, and sphericity. For acicular minerals like wollastonite, these parameters are essential for correlating morphology with functional properties.

Standard Methods

  • ISO 13322-2: Particle size analysis — Image analysis methods
  • ISO 13320: Laser diffraction methods (complementary for size distribution)>

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